In an age filled with advanced medical techniques like MRIs, artificial hearts, and laser eye surgery, one could be forgiven for believing doctors are also at least vaguely familiar with every one of your body parts. However, a new discovery by Belgian physicians has proved this assumption wrong.

As Science Dailyreports, two surgeons at University Hospitals Leuven have located a new ligament in the human knee, and their findings may mean a revolution in how we treat ACL injuries. Dr. Steven Claes and Professor Dr. Johan Bellemans have spent four years trying to solve a modern medical mystery: in certain cases, patients who have had their ACL repaired still experience “pivot shifts” in their knee, where the joint “gives way” during physical activity.

In order to find their answer, the scientists turned to the past. In an 1879 article, a French surgeon theorized that there may exist an extra ligament in the anterior of the human knee. Using macroscopic dissection techniques on a wide range of cadavers, the Belgian duo confirmed this hypothesis. According to their findings, 97 percent of humans have something called an anterolateral ligament (ALL) in addition to their ACL, and pivot shifts stem from an injury to this previously unknown body part.

This discovery could mean a breakthrough in treating ACL injuries, which are common in sports like basketball, football, and soccer, where pivoting is common — but don’t hold your breath for a better fix. Claes and Bellemans are hard at work figuring out surgical to techniques to repair the ALL, but Science Daily cautions that those results will only be ready in “several years.”

To me, this just seems ridiculous! I mean, sports injuries to the knee have been treated for a very long time, how could they miss an entire ligament? Is it like, super thin and just blends in with another nearby ligament? I don't get this at all!

Guess it will help people eventually. I find it interesting though, that some brilliant guy over 140 years ago suggested it was there?

There are many mysteries left in the human body! I was born with an extra set of ribs one vertebrae higher than almost everyone else. Called "cervical ribs" because they are on cervical sections of the spine, for a lot of people who have them they are small and cause no problems. I wasn't so lucky! It took 2 surgeries to remove most of the extra bone encroaching on nerves and blood vessels to my arms to restore feeling and blood flow. Just a few months ago I was giving my "what are you here for" explanation to a nurse in preparation for a doctor's office call and when I suggested that the scar on my neck (the first one, done on Okinawa in 1966 before this was well understood - they go in under the arm now) was from removal of an extra rib. The nurse backed up a couple of steps and haughtily announced that people are NOT born with 13 sets of ribs, and walked out of the room apparently assuming that I was being dishonest. Hmm. . . . . Keep an open mind!

This article is poor research and even worse media reporting. The researchers basically took the work of others and gave it a new name. This ligament or whatever you want to call it, was discovered and studies long ago. There is nothing shocking or new here. The researchers quibbled over small details. They claim knee injury risk, however they performed ZERO such measures. They theorized, but provided no anterior translation tests, lateral pivots shifts, Lachman's, etc. Furthermore, they omitted major aspects in their discussion. For instance they claimed the Vincent (2012) article only included inconclusive diagrams. WRONG!!! There is a full color cadaver photo with clearly labeled structure sitting right next to the drawing. Actually, if you read the Vincent (2012) article you will find a much more in-depth study that said THE EXACT SAME THING! This whole study is nothing but a re-branding of previous know information with very little new significant information.

It amazes me to learn that there is still uncertainty about how specific ligaments hold the knee joint together and make it capable of supporting the body in various positions and with different kinds of motions.

Dr. Robert LaPrade, Chief Medical Officer at the Steadman Philippon Research Institute and expert on sports related complex knee injuries at The Steadman Clinic in Vail, Colorado has posted some additional information on the history of research on this ligament on his website.

He says, "The structure that Dr. Claes refers to as the anterolateral ligament has been called other names in the past. His group has gone into a much more detailed description of this ligament...In the past, Dr. Ron Losse reconstructed the structure that Dr. Claes is referring to as the "ALL." The attachment points for the graft that Dr. Losse described coincides exactly with the location of Dr. Claes and his group's description of the ALL. In addition, his structure coincides with a thickening of what Dr. Jack Hughston called the mid-third lateral capsular ligament.

All of these investigators, as well as others at other centers, have reported that this ligament is important in providing some stability to the knee. To date, we as a profession have not completely defined what all the structures around the knee do in providing stability to the knee."

@michael.e.lovett I would go further. After hundreds of millions of X-rays, MRIs, CAT scans, dissections, autopsies, surgeries (as you point out, particularly in sports, where professional sports doctors know every molecule of the knee), etc. - over a period of at least 100 years - NOT ONE SINGLE PERSON actually found and identified this ligament?!?!?!

@jerryabr It's actually not shown in the image at all. They lazily used a stock photo instead of a photo from the actual journal article. This image shows the posterior aspect of the knee joint, including the MCL, medial meniscus, PCL, ACL, ligament of Humphrey, ligament of Wrisberg, lateral meniscus, and LCL. The ALL is nowhere to be seen.

@MomWizCom that's not a mystery, that's a deformity. A mystery is something unknown and since very few people are born with "cervical ribs", and doctors and other have seen this before, that isn't considered a mystery. Do you consider someone born with extra fingers a mystery? No, it's a deformity and your genes are sub par.

@MomWizCom There was a professional baseball player (I cannot remember his name) with the same condition. He began having all kinds of problems with his throwing arm. It was that extra rib pressing on nerves and arteries. Once it was removed, he recovered and went back to baseball. The condition is an interesting example of human evolution. Within vertebrates, there has been a reduction in the number of ribs (think about how many ribs a snakes has). We evidently still have genes to express more than 12 ribs, they are usually just not expressed in most humans.

@DavidBaumgardner You might be thinking of Chris Carpenter of the St. Louis Cardinals. He was diagnosed with thoracic outlet syndrome in 2012. He had surgery to remove a rib in July 2012 and returned to the mound in September 2012. He pitched few games in the postseason, but the symptoms returned in spring training this past year and he was out for the year.

@rfalcon1000@psutooba It DOES matter, because things are always forgotten (or never learned) and then rediscovered by the internet press and touted as a new thing which cheapens basic knowledge. The fact that you dismiss the comment so flippantly shows we are closer to a society of unconcerned phone zombies as one would like to think,

@rfalcon1000@psutooba To the public, no it doesn't matter. To the research community, who discovers what, and when they discover it, is paramount. Jobs, promotions, raises, prestige, grants, and even Nobels (though not for this) depend on these "petty" details. But even if you can't understand the finer points of the profession, then limit yourself to the OP's first sentence. The article fails to report anything substantive, and what it does report is fundamentally not new, so then why bother to report it? Poor journalism. And that's something that should bother you.